Miniaturised relay and corresponding uses thereof

ABSTRACT

A miniaturized relay having a first zone facing a second zone, a first condenser plate, a second condenser plate arranged in the second zone, and smaller than or equal to the first plate, an intermediate space between both zones, a conductive element arranged in the intermediate space and which is mechanically independent from the adjacent walls and can move freely across the intermediate space depending on voltages present between both plates, contact points of an electric circuit, in which the conductive element closes the electric circuit by making contact with the contact points. Such relays can be used, for example, as: accelerometers, accelerometers in airbags, tiltmeters, Coriolis force detectors, microphones, in acoustic applications, pressure sensors, flow sensors, temperature sensors, gas sensors and magnetic field sensors.

FIELD OF THE INVENTION

This invention relates to a miniaturised relay. The invention alsorefers to different uses for miniaturised relays according to theinvention.

STATE OF THE ART

Currently there are various alternatives for the production ofminiaturised relays, in particular, in the context of technologies knownas MEMS technology (micro electromechanical systems), Microsystemsand/or Micromachines. In principal such may be classified according tothe type of force or actuation mechanism they use to move the contactelectrode. The classification usually applied is thus betweenelectrostatic, magnetic, thermal and piezoelectric relays. Each one hasits advantages and its drawbacks. However miniaturisation techniquesrequire the use of activation voltages and surfaces which are as smallas possible. Relays known in the state of the art have several problemsimpeding their advance in this respect.

A manner of reducing the activation voltage is precisely to increase therelay surface areas, which renders miniaturisation difficult, apart frombeing conducive to the appearance of deformations reducing the usefullife and reliability of the relay. In electrostatic relays, anothersolution for decreasing the activation voltage is to greatly reduce thespace between the electrodes, or use very thin electrodes or specialmaterials, so that the mechanical recovery force is very low. Howeverthis implies problems of sticking, since capillary forces are very high,which thus also reduces the useful working life and reliability of theserelays. The use of high activation voltages also has negative effectssuch as ionisation of the components, accelerated wearing due to strongmechanical solicitation and the electric noise which the relaygenerates.

Electrostatic relays also have a significant problem as to reliability,due to the phenomenon known as “pull-in”, and which consists in that,once a given threshold has been passed, the contact electrode moves inincreasing acceleration against the other free electrode. This is due tothe fact that as the relay closes, the condenser which exerts theelectrostatic force for closing, greatly increases its capacity (andwould increase to infinity if a stop were not imposed beforehand).Consequently there is a significant wear on the electrodes due to thehigh electric field which is generated and the shock caused by theacceleration to which the moving electrode has been exposed.

Thermal, magnetic and piezoelectric approaches require special materialsand micromachined processes, and thus integration in more complex MEMSdevices, or in a same integrated with electronic circuitry is difficultand/or costly. Additionally the thermal approach is very slow (which isto say that the circuit has a long opening or closing time) and uses agreat deal of power. The magnetic approach generates electromagneticnoise, which renders having close electronic circuitry much moredifficult, and requires high peak currents for switching.

In this specification relay should be understood to be any devicesuitable for opening and closing at least one external electric circuit,in which at least one of the external electric circuit opening andclosing actions is performed by means of an electromagnetic signal.

In the present description and claims the expression “contact point” hasbeen used to refer to contact surfaces in which an electric contact ismade (or can be made). In this respect they should not be understood aspoints in the geometric sense, since they are three-dimensionalelements, but rather in the electric sense, as points in an electriccircuit.

SUMMARY OF THE INVENTION

The objective of the present invention is to overcome the abovementioneddrawbacks. This is achieved by means of a miniaturised relaycharacterised in that it comprises:

a first zone facing a second zone,

a first condenser plate,

a second condenser plate arranged in the second zone, in which thesecond plate is smaller than or equal to the first plate,

an intermediate space arranged between the first zone and the secondzone,

a conductive element arranged in the intermediate space, the conductiveelement being mechanically independent of the first zone and the secondzone and being suitable for performing a movement across theintermediate space dependant on voltages present in the first and secondcondenser plates,

a first contact point of an electric circuit, a second contact point ofthe electric circuit, in which the first and second contact point definefirst stops, in which the conductive element is suitable for enteringinto contact with the first stops and in which the conductive elementcloses the electric circuit when in contact with the first stops.

In fact in the relay according to the invention the conductive element,which is to say the element responsible for opening and closing theexternal electric circuit (across the first contact point and the secondcontact point), is a detached part capable of moving freely. I.e. theelastic force of the material is not being used to force one of therelay movements. This allows a plurality of different solutions, allbenefiting from the advantage of needing very low activation voltagesand allowing very small design sizes. The conductive element is housedin the intermediate space. The intermediate space is closed by the firstand second zone and by lateral walls which prevent the conductiveelement from leaving the intermediate space. When voltage is applied tothe first and second condenser plate charge distributions are induced inthe conductive element which generates electrostatic forces which inturn move the conductive element in a direction along the intermediatespace. By means of different designs to be described in detail belowthis effect can be used in several different ways.

Additionally, a relay according to the invention likewise satisfactorilyresolves the previously mentioned problem of “pull-in”.

Another additional advantage of the relay according to the invention isthe following: in conventional electrostatic relays, if the conductiveelement sticks in a given position (which depends to a great extent,among other factors, on the humidity) there is no possible manner ofunsticking it (except by external means, such as for example drying it)since due to the fact that the recovery force is elastic, is always thesame (depending only on the position) and cannot be increased. On thecontrary, if the conductive element sticks in a relay according to theinvention, it will always be possible to unstick it by increasing thevoltage.

The function of the geometry of the intermediate space and thepositioning of the condenser plates can furnish several different typesof relays, with as many applications and functioning methods.

For example, the movement of the conductive element can be as follows:

a first possibility is that the conductive element move along theintermediate space with a travelling movement, i.e., in a substantiallyrectilinear manner (excluding of course possible shocks or oscillationsand/or movements provoked by unplanned and undesired external forces)between the first and second zones.

a second possibility is that the conductive element have a substantiallyfixed end, around which can rotate the conductive element. Therotational axis can serve the function of contact point for the externalelectric circuit and the free end of the conductive element can movebetween the first and second zones and make, or not make, contact withthe other contact point, depending on its position. As will be outlinedbelow, this approach has a range of specific advantages.

a third possibility is that the conductive element move along theintermediate space with a movement that combines a travelling movementbetween the first and second zones, induced by the electrostatic forcesgenerated, and a movement that is perpendicular to the former, inducedby a Coriolis force. This solution will be described in greater detailbelow.

Advantageously the first contact point is between the second zone andthe conductive element. This allows a range of solutions to be obtained,discussed below.

A preferable embodiment is achieved when the first plate is in thesecond zone. Alternatively the relay can be designed so that the firstplate is in the first zone. In the first case a relay is obtained whichhas a greater activation voltage and which is faster. On the other hand,in the second case the relay is slower, which means that the shocksexperienced by the conductive element and the stops are smoother, andenergy consumption is lower. One can obviously choose between one or theother alternatives depending on the specific requirements in each case.

A preferable embodiment of the invention is obtained when the secondcontact point is likewise in the second zone. In this case one will havea relay in which the conductive element performs the substantiallyrectilinear travelling movement. When the conductive element is incontact with the first stops, which is to say with the first and secondcontact point of the electric circuit, the electric circuit is closed,and it is possible to open the electric circuit by means of differenttypes of forces, detailed below. To again close the electric circuit, itis enough to apply voltage between the first and second condenserplates. This causes the conductive element to be attracted toward thesecond zone, again contacting the first and second contact point.

Should the fist condenser plate be in the first zone and the secondcondenser plate in the second zone, a manner of achieving the necessaryforce to open the circuit cited in the above paragraph is by means ofthe addition of a third condenser plate arranged in the second zone, inwhich the third condenser plate is smaller than or equal to the firstcondenser plate, and in which the second and third condenser plates are,together, larger than the first condenser plate. With this arrangementthe first condenser plate is to one side of the intermediate space andthe second and third condenser plates are to the other side of theintermediate space and close to one another. In this manner one canforce the movement of the conductive element in both directions by meansof electrostatic forces and, in addition, one can guarantee the closingof the external electric circuit even though the conductor elementremains at a voltage in principle unknown, which will be forced by theexternal circuit that is closed.

Another preferable embodiment of the invention is achieved when therelay additionally comprises a third condenser plate arranged in saidsecond zone and a fourth condenser plate arranged in said first zone, inwhich said first condenser plate and said second condenser plate areequal to each other, and said third condenser plate and said fourthcondenser plate are equal to one another. In fact, in this manner, ifone wishes the conductive element to travel towards the second zone, onecan apply voltage to the first and fourth condenser plates, on one side,and to the second or to the third condenser plates, on the other side.Given that the conductive element will move toward the place in which islocated the smallest condenser plate, it will move toward the secondzone. Likewise one can obtain movement of the conductive element towardthe first zone by applying a voltage to the second and third condenserplates and to the first or the fourth condenser plates. The advantage ofthis solution, over the simpler three condenser plate solution, is thatit is totally symmetrical, which is to say that it achieves exactly thesame relay behaviour irrespective of whether the conductive elementmoves toward the second zone or the first zone. Advantageously thefirst, second, third and fourth condenser plates are all equal withrespect to one another, since generally it is convenient that in itsdesign the relay be symmetrical in several respects. On one hand thereis symmetry between the first and second zone, as commented above. Onthe other hand it is necessary to retain other types of symmetry toavoid other problems, such as for example the problems of rotation orswinging in the conductive element and which will be commented uponbelow. In this respect it is particularly advantageous that the relaycomprise, additionally, a fifth condenser plate arranged in the firstzone and a sixth condenser plate arranged in the second zone, in whichthe fifth condenser plate and the sixth condenser plate are equal toeach other. On one hand increasing the number of condenser plates hasthe advantage of better compensating manufacturing variations. On theother, the several different plates can be activated independently, bothfrom the point of view of voltage applied as of activation time. The sixcondenser plates can all be equal to each other, or alternatively thethree plates of a same side can have different sizes with respect to oneanother. This allows minimising activation voltages. A relay which hasthree or more condenser plates in each zone allows the followingobjectives to all be achieved:

it can function in both directions symmetrically,

it has a design which allows a minimum activation voltage for fixedoverall relay dimensions, since by having two plates active in one zoneand one plate active in the other zone distinct surface areas can alwaysbe provided,

it allows minimisation of current and power consumption, and also asmoother relay functioning,

it can guarantee the opening and closing of the relay, independently ofthe voltage transmitted by the external electric circuit to theconductive element when they enter in contact,

in particular if the relay has six condenser plates in each zone, it canin addition comply with the requirement of central symmetry which, as weshall see below, is another significant advantage. Therefore anotherpreferable embodiment of the invention is obtained when the relaycomprises six condenser plates arranged in the first zone and sixcondenser plates arranged in the second zone. However it is notabsolutely necessary to have six condenser plates in each zone toachieve central symmetry: it is possible to achieve it as well, forexample, with three condenser plates in each zone, although in this caseone must forego minimising current and power consumption and optimisingthe “smooth” functioning of the relay. In general, increasing the numberof condenser plates in each zone allows greater flexibility andversatility in the design, whilst it allows a reduction of thevariations inherent in manufacture, since the manufacturing variationsof each of the plates will tend to be compensated by the variations ofthe remaining plates.

However it should not be discounted that in certain cases it can beinteresting to deliberately provoke the existence of force moments inorder to force the conductive element to perform some kind of revolutionadditional to the travelling movement. It could be advantageous, forexample, to overcome possible sticking or friction of the conductiveelement with respect to the fixed walls.

Advantageously the relay comprises a second stop (or as many secondstops as there are first stops) between the first zone and theconductive element. In this manner one also achieves a geometricsymmetry between the first zone and the second zone. When the conductiveelement moves toward the second zone, it can do so until entering intocontact with the first stops, and will close the external electriccircuit. When the conductive element moves toward the first zone it cando so until entering into contact with the second stop(s). In thismanner the movement performed by the conductive element is symmetrical.

Another preferable embodiment of the invention is achieved when therelay comprises a third contact point arranged between the first zoneand the conductive element, in which the third contact point defines asecond stop, such that the conductive element closes a second electriccircuit when in contact with the second contact point and third contactpoint. In this case the relay acts as a commuter, alternately connectingthe second contact point with the first contact point and with the thirdcontact point.

A particularly advantageous embodiment of the previous example isachieved when the conductive element comprises a hollow cylindrical partwhich defines a axis, in the interior of which is housed the secondcontact point, and a flat part which protrudes from one side of theradially hollow cylindrical part and which extends in the direction ofthe axis, in which the flat part has a height, measured in the directionof the axis, which is less than the height of the cylindrical part,measured in the direction of the axis. This specific case compliessimultaneously with the circumstance that the conductive element performa rotational movement around one of its ends (cf. the “secondpossibility” cited above). Additionally, the cylindrical part is thatwhich rests on bearing surfaces (one at each end of the cylinder, andwhich extends between the first zone and the second zone) whilst theflat part is cantilevered with respect to the cylindrical part, since ithas a lesser height. Thus the flat part is not in contact with walls orfixed surfaces (except the first and third contact point) and, in thismanner, the sticking and frictional forces are lessened. As to thesecond point of contact, it is housed in the internal part of thecylindrical part, and serves as rotational axis as well as secondcontact point. Thus an electric connection is established between thefirst and second contact points or between the third and second contactpoints. The hollow cylindrical part defines a cylindrical hollow, whichin all cases has a surface curved to the second contact point, thusreducing the risks of sticking and frictional forces.

Another particularly advantageous embodiment of the previous example isobtained when the conductive element comprises a hollow parallelepipedicpart which defines a axis, in the interior of which is housed the secondcontact point, and a flat part which protrudes from one side of theradially hollow paralelepipedic part and which extends in the directionof the axis, in which the flat part has a height, measured in thedirection of the axis, which is less than the height of theparallelepipedic part, measured in the direction of the axis. In fact,it is an embodiment similar to that above, in which the parallelepipedicpart defines a parallelepipedic hollow. This solution can beparticularly advantageous in the case of very small embodiments, sincein this case the resolution capacity of the manufacturing process (inparticular in the case of the photolithographic procedures) obliges theuse of straight lines. In both cases it should be emphasised that thedetermining geometry is the geometry of the interior hollow and that, infact, several different combinations are possible:

axis (second contact point) having a rectangular section and hollow withrectangular section,

axis having a circular section and hollow having a circular section,

axis having a circular section and hollow having a rectangular sectionand vice versa,

although the first two combinations are the most advantageous.

Logically, should the sections be rectangular, there should be enoughplay between the axis and the parallelepipedic part such that theconductive element can rotate around the axis. Likewise in the case ofcircular sections there can be a significant amount of play between theaxis and the cylindrical part, such that the real movement performed bythe conductive element is a combination of rotation around the axis andtravel between the first and second zone. It should be noted,additionally, that it is also possible that the second stop not beconnected electrically to any electric circuit: in this case a relaywill be obtained which can open and close only one electric circuit, butin which the conductive element moves by means of a rotation (or bymeans of a rotation combined with travel).

Another preferable embodiment of the invention is obtained when therelay comprises a third and a fourth contact points arranged between thefirst zone and the conductive element, in which the third and fourthcontact points define second stops, such that the conductive elementcloses a second electric circuit when in contact with the third andfourth contact points. In fact, in this case the relay can alternativelyconnect two electric circuits.

Advantageously each of the assemblies of condenser plates arranged ineach of the first zone and second zone is centrally symmetrical withrespect to a centre of symmetry, in which said centre of symmetry issuperposed to the centre of masses of the conductive element. In fact,each assembly of the condenser plates arranged in each of the zonesgenerates a field of forces on the conductive element. If the forceresulting from this field of forces has a non nil moment with respect tothe centre of masses of the conductive element, the conductive elementwill not only undergo travel but will also undergo rotation around itscentre of masses. In this respect it is suitable to provide that theassemblies of plates of each zone have central symmetry in the case thatthis rotation is not advantageous, or on the other hand it could beconvenient to provide central asymmetry should it be advantageous toinduce rotation in the conductive element with respect to its centre ofmasses, for example to overcome frictional forces and/or sticking.

As already indicated, the conductive element is usually physicallyenclosed in the intermediate space, between the first zone, the secondzone and lateral walls. Advantageously between the lateral walls and theconductive element there is play sufficiently small such as togeometrically prevent the conductive element entering into contactsimultaneously with a contact point of the group formed by the first andsecond contact points and with a contact point of the group formed bythe third and fourth contact points. That is to say, the conductiveelement is prevented from adopting a transversal position in theintermediate space in which it connects the first electric circuit tothe second electric circuit.

To avoid sticking and high frictional forces it is advantageous that theconductive element have rounded external surfaces, preferably that it becylindrical or spherical. The spherical solution minimises thefrictional forces and sticking in all directions, whilst the cylindricalsolution, with the bases of the cylinder facing the first and secondzone allow reduced frictional forces to be achieved with respect to thelateral walls whilst having large surfaces facing the condenserplates—efficient as concerns generation of electrostatic forces. Thissecond solution also has larger contact surfaces with the contactpoints, diminishing the electric resistance which is introduced in thecommuted electric circuit.

Likewise, should the conductive element have an upper face and a lowerface, which are perpendicular to the movement of the conductive element,and at least one lateral face, it is advantageous that the lateral facehave slight protuberances. These protuberances will further allowreduction of sticking and frictional forces between the lateral face andthe lateral walls of the intermediate space.

Advantageously the conductive element is hollow. This allows reducedmass and thus achieves lower inertia.

Should the relay have two condenser plates (the first plate and thesecond plate) and both in the second zone, it is advantageous that thefirst condenser plate and the second condenser plate have the samesurface area, since in this manner the minimal activation voltage isobtained for a same total device surface area.

Should the relay have two condenser plates (the first plate and thesecond plate) and the first plate is in the first zone whilst the secondplate is in the second zone, it is advantageous that the first condenserplate has a surface area that is equal to double the surface area of thesecond condenser plate, since in this manner the minimal activationvoltage is obtained for a same total device surface area.

Another preferable embodiment of a relay according to the invention isobtained when one of the condenser plates simultaneously serves ascondenser plate and as contact point (and thus of stop). Thisarrangement will allow connection of the other contact point (that ofthe external electric circuit) at a fixed voltage (normally VCC or GND)or leaving it at high impedance.

The subject of the invention likewise relates to preferential uses forrelays according to the invention. Apart from use as electric switch andas electric commuter, the relay according to the invention can be usedas a sensor for different physical magnitudes. In such cases, thephysical magnitude which one wishes to measure exerts a force to openthe electric circuit and by means of a given voltage applied to thecondenser plates a force is generated which counteracts the former andthe external electric circuit is again closed (or vice versa, i.e., itis necessary to apply a voltage to maintain the electric circuit openwhilst the physical magnitude which one wishes to study tends to closethe circuit). The determination of the voltage required allowsdetermination of the physical magnitude one wishes to measure. Ingeneral, miniaturisation allows the inclusion of several sensorssimultaneously, which increases the reliability of the correspondingdetermination. The increase in reliability is due to the possibilitythat these different sensors measure the same magnitude, andsubsequently one calculates the mean. A particularly advantageousalternative is obtained by arranging a relay according to the inventionwith electric contacts in both zones, i.e. three or four contacts intotal, since in this case one can measure the physical magnitude understudy from the time lapsed between interruption of the contact with theelectric contact(s) in one zone and the establishment of the electriccontact with the electric contact(s) of the other zone, at constantvoltage (or even varying the voltage as a further parameter to beaccounted for). Below are provided various specific examples:

Accelerometer: the force due to outside acceleration moves theconductive element, opening the electric circuit. The voltage applied tothe condenser plates creates an opposing force. When the circuit againcloses the voltage required can be determined and thus, the accelerationto which the conductive element has been subjected. This can also takeplace in reverse, such as commented upon above, the outside accelerationbeing that which tends to close the circuit. Miniaturisation allowsprovision of various sensors, orientated according to the threecoordinate axes. Specific examples would be airbags and tiltmeters.

Pressure sensor: if the electric element separates two chamberssubjected to different pressures (a pressure to be determined and areference pressure), air pressure, or in general any other nonconducting fluid, applied to one of the faces of the conductive elementwould tend to open (or close) the electric circuit. The voltagenecessary to again achieve closing (opening) of the circuit allowsmeasure of the pressure of said fluid or, specifically, the differenceof pressure between said fluid and the reference chamber. A specificexample of this type of sensor would be a microphone.

Flow sensor: if the conductive element has an aperture through which canpass a current of fluid or if it has an extension which is immersed in acurrent of fluid, a relay according to the invention can be used as flowsensor. As in the above examples, by means of a given voltage applied tothe condenser plates one can counteract the force generated by thephysical magnitude one wishes to measure, in this case the hydraulic oraerodynamic force generated by the fluid current. As in the above caseconcerning the pressure sensor, the fluid cannot however be anelectrical conductor.

Temperature sensor. In this case it should be taken into account thatthe time the relay takes to switch basically depends upon externalacceleration, voltage applied and the surface area coefficients of thecondenser plates. If these plates are made from materials havingdifferent thermal expansion coefficients, the surface area coefficientsof the condenser plates will change with temperature. In this mannerthere is a relationship between the switching time and the temperaturewith respect to a given voltage applied to the plates. Similarly theminimum voltage necessary to switch the relay will depend on thetemperature.

Acoustic applications (loudspeakers). In colliding with the stops oragainst the condenser plates which attract it, the conductive elementwill produce noise. By co-ordinating a significant number of relays,which can be integrated in a single chip, one can gather the differentacoustic waves together in phase and thus create a resulting acousticwave that is audible. This audible acoustic wave will be highlydirectional. This can be an advantage when what is wanted isunidirectional waves; alternatively the relays can be distributed and/oractivated in different directions and/or dephased with respect to timeto obtain a multidirectional wave. It is also possible to controldirectionality by controlling the precise moment in which each relay isactivated, which is to say, by controlling the relative temporaldephases between the relays. In this manner one can dynamically changethe directionality of the acoustic wave, so that it can be directedaccording to requirements without having to change the geometricdistribution of the relays. The presence of the electric contacts allowsa determination of the exact moment in which the shock of the conductiveelement with the corresponding stops takes place.

Detector of Coriolis forces (usually known as gyrostats). Thesedetectors determine the rotational speed of an object by determining theCoriolis force. To do so one needs a relay having condenser platesarranged in the first zone and in the second zone, and contact pointsarranged in an axis perpendicular to the first zone-second zone axis.The conductive element should be in continual movement from one end tothe other so that it is always provided with a given velocity, whichwill depend on the voltage applied to the condenser plates. If there isa rotational velocity which is perpendicular to the plane formed by theaxis of movement (first zone-second zone axis), and the contact points,then the conductive element will experience Coriolis acceleration whichwill be perpendicular to the first zone-second zone axis. This will meanthat the conductive element touches the contact points of one side (orof the opposite side, depending on the rotational direction) if thevoltage applied to the condenser plates and, thus, the speed with whichthe conductive element moves, is sufficiently high. In touching thecontact points the external circuit will be closed thus confirming thatthe conditions necessary for such have been obtained. The magnitude ofthe external rotation will be, thus, related with the magnitude of thevoltage applied to the condenser plates, and the rotational directioncan be known based on which of the two pairs of contacts has beenshort-circuited, taking into account the direction of the velocity beingproportioned at such time to the conductive element. Sensors of thistype can be included simultaneously in three perpendicular directions,which allows any rotation in space to be determined.

Gas sensor. Should the conductive element be of a material capable ofreacting and/or absorbing molecules of a given gas (or should suchmaterial be incorporated in the conductive element) a conductive elementis obtained having a variable mass depending on the concentration ofsaid gas. This change in mass influences the activation voltage, as wellas the time lapse in moving from one end to another. Gas concentrationcan thus be determined.

In general, in all sensors cited above one can determine thecorresponding magnitude by detecting in each case what is the minimumvoltage necessary to switch the relay, or detect which is the switchingtime for a fixed applied voltage. In general it is easier to detect theswitching time, since it can be increased very simply using digitaltechnology, whilst generating variable voltages implies using analogcircuits. However when detecting the voltage which switches the relay,there is the advantage that the relay is required to switch much lessfrequently, reducing wear and increasing long term reliability andworking life.

Another possible application of a relay according to the invention is asmagnetic field detector. For such the relay must be maintained in itsclosed position, i.e. with the conductive element closing the firstexternal electric circuit, and a current with a certain intensity shouldbe passed through the conductive element. If the relay is subjected to amagnetic field, the conductive element will be subjected to a magneticforce and, if the direction is suitable, this magnetic force will tendto open the electric circuit. By determining the voltage necessary tomaintain the electric circuit closed and taking into account otherparameters (geometry and mass of the conductive element, currentintensity through it, etc.) one can determine a spatial component of themagnetic field and in a given direction. If one provides a plurality ofsensors orientated in space such that all spatial components of themagnetic field can be determined, the entire magnetic field can bedetermined. If the relay has electric contact points both in the firstzone and in the second, such that two external electric circuits can beclosed, then with one relay a spatial component of the magnetic fieldcan be determined, irrespective of its direction, since if theconductive element is in one zone, the magnetic field will tend to pressit against the contact points instead of separating it, placing theconductive element in the opposite zone the magnetic field will tend toseparate it from the contact points, and thus determination is possible.Knowing which of the electric circuits was used for said determinationgives the direction. It should be observed that, to use the relay asmagnetic field detector the electric circuit should be closed and asufficiently high electric current should be passed through theconductive element for it to experience the corresponding magneticforce. In fact, when the magnetic field opens the electric circuit,electric current will cease to pass through the conductive element andthe magnetic force will disappear, and thus the conductive element willagain come into contact with the electric contact points, since theelectrostatic field will remain active. Some time should thus be allowedto run before re-establishing the electric current and the conductiveelement again experiences the magnetic force. To differentiate themagnetic force which the conductive element experiences from otherexternal accelerations, the magnetic field sensor could include severalrelays, some responsible for detecting the magnetic force as outlinedabove, and others for measuring accelerations as described above in therelevant section. By compensating the results obtained for eachcomponent the real magnetic field can be determined. Alternatively, oneand the same relay can perform magnetic field readings (by provoking thepassage of current through the conductive element) interspersed withacceleration readings (in which current is not passed through theconductive element).

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages and characteristics of the invention will becomeevident from the following description in which, entirelynon-limitatively, are described some preferential embodiments of theinvention, with reference to the appended drawings. The figures show:

FIG. 1, a simplified diagram of a relay with two condenser plates in thesecond zone thereof;

FIG. 2, a simplified diagram of a relay with two condenser plates, onein each of the zones thereof;

FIG. 3, a simplified diagram of a relay with three condenser plates;

FIG. 4, a perspective view of a first embodiment of a relay according tothe invention, uncovered;

FIG. 5, a plan view of the relay of FIG. 4;

FIG. 6, a perspective view of a second embodiment of a relay accordingto the invention;

FIG. 7, a perspective view of the relay of FIG. 6 from which thecomponents of the upper end have been removed;

FIG. 8, a perspective view of the lower elements of the relay of FIG. 6;

FIG. 9, a perspective view of a third embodiment of a relay according tothe invention, uncovered;

FIG. 10, a perspective view, in detail, of the cylindrical part of therelay of FIG. 9;

FIG. 11, a perspective view of a fourth embodiment of a relay accordingto the invention;

FIG. 12, a perspective view of a fifth embodiment of a relay accordingto the invention;

FIG. 13, a plan view of a sixth embodiment of a relay according to theinvention;

FIG. 14, a perspective view of a seventh embodiment of a relay accordingto the invention;

FIG. 15, a perspective view from below, without substrate, of an eighthembodiment of a relay according to the invention;

FIG. 16, a sphere produced with surface micromachining;

FIG. 17, a perspective view of a ninth embodiment of a relay accordingto the invention; and

FIG. 18, a plan view, uncovered, of a tenth embodiment of a relayaccording to the invention.

As shall be seen below, the preferred embodiments of the inventionillustrated in the figures include a combination of the severaldifferent alternatives and options considered above, whilst a personskilled in the art will be able to see what alternatives and options canbe combined together in different ways.

DETAILED DESCRIPTION OF SOME EMBODIMENTS OF THE INVENTION

FIG. 1 shows a first basic functioning mode of a relay according to theinvention. The relay defines an intermediate space 25 in which is houseda conductive element 7, which can move freely along the intermediatespace 25, since physically it is a detached part which is not physicallyjoined to the walls which define the intermediate space 25. The relayalso defines a first zone, on the left in FIG. 1, and a second zone, onthe right in FIG. 1. In the second zone are arranged a first condenserplate 3 and a second condenser plate 9. In the example shown in FIG. 1both condenser plates 3 and 9 have different surface areas, althoughthey can be equal with respect to one another. The first condenser plate3 and the second condenser plate 9 are connected to a CC controlcircuit. Applying a voltage between the first condenser plate 3 and thesecond condenser plate 9, the conductive element is always attractedtowards the right in FIG. 1, towards the condenser plates 3 and 9. Theconductive element 7 will be moved towards the right until being stoppedby first stops 13, which are a first contact point 15 and a secondcontact point 17 of a first external electric circuit CE1, such that thefirst external electric circuit CE1 is closed.

FIG. 2 shows a second basic functioning mode for a relay according tothe invention. The relay again defines an intermediate space 25 in whichis housed a conductive element 7, which can move freely along theintermediate space 25, a first zone, on the left in FIG. 2, and a secondzone, on the right in FIG. 2. In the second zone is arranged a secondcondenser plate 9 whilst in the first zone is arranged a first condenserplate 3. The first condenser plate 3 and the second condenser plate 9are connected to a CC control circuit. Applying a voltage between thefirst condenser plate 3 and the second condenser plate 9, the conductiveelement is always attracted to the right of the FIG. 2, towards thesmallest condenser plate, i.e. towards the second condenser plate 9. Forthis reason, the fact that in the example shown in FIG. 2 both condenserplates 3 and 9 have different surface areas is, in this case, absolutelynecessary, since if they were to have equal surface areas, theconductive element 7 would not move in any direction. The conductiveelement 7 will move towards the right until being stopped by first stops13, which are a first contact point 15 and a second contact point 17 ofa first external electric circuit CE1, such that the first externalelectric circuit CE1 is closed. On the left there are second stops 19which in this case do not serve any electric function but which stop theconductive element 7 from entering into contact with the first condenserplate 3. In this case the stops 19 can be removed, since no problem isposed by the conductive element 7 entering into contact with the firstcondenser plate 3. This is because there is only one condenser plate onthis side, if there had been more than one and if they had beenconnected to different voltages then the stops would have been necessaryto avoid a short-circuit.

The configurations of the relays of FIGS. 1 and 2 are suitable for beingused as sensors, in which the magnitude to be measured exercises a forcewhich is that which will be counteracted by the electrostatic forceinduced in the conductive element 7. Such as represented, in both casesthe magnitude to be measured must exercise a force tending to open theelectric circuit CE1, whilst the electrostatic force will tend to closeit. However, a relay can be designed to work exactly in the oppositerespect: such that the magnitude to be measured would tend to close theelectric circuit CE1 whilst the electrostatic force would tend to openit. In this case, the first stops 13 would need to be positioned on theleft in FIGS. 1 and 2, together with the corresponding electric circuitCE1. In FIG. 1 this possibility has been shown in a broken line. If thestops are placed on both sides then the sensor can detect magnitude inboth directions, although the algorithm would have to change, fromtending to close to tending to open, when a change in direction isdetected as having occurred, as would happen when not obtainingclosing/opening with the minimum voltage, which is zero. It should berecalled that the sign of the voltage applied does not effect thedirection of movement of the conductive element 7.

To achieve moving the conductive element 7 in both directions by meansof electrostatic forces, it is necessary to provide a third condenserplate 11, as shown in FIG. 3. Given that the conductive element 7 willalways move towards where the smallest condenser plate is located, it isnecessary, in this case, that the third condenser plate 11 be smallerthan the first condenser plate 3, but that the sum of the surface areasof the second condenser plate 9 and the third condenser plate 11 belarger than the first condenser plate 3. In this manner, activating thefirst condenser plate 3 and the second condenser plate 9, connectingthem to different voltages, but not the third condenser plate 11, whichwill remain in a state of high impedance, the conductive element 7 canbe moved to the right, whilst activating the three condenser plates 3, 9and 11 the conductor element 7 can be moved to the left. In the lattercase the second condenser plate 9 and the third condenser plate 11 aresupplied at a same voltage, and the first condenser plate 3 at adifferent voltage. The relay of FIG. 3 has, in addition, a secondexternal electric circuit CE2 connected to the second stops 19, in amanner that these second stops 19 define a third contact point 21 and afourth contact point 23.

Should two condenser plates be provided in each of the first and secondzones, the movement of the conductive element 7 can be solicited in twodifferent ways:

applying a voltage between the two condenser plates of a same zone, sothat the conductive element is attracted by them (functioning as in FIG.1)

applying a voltage between one condenser plate of one zone and a (orboth) condenser plate(s) of the other zone, such that the conductiveelement 7 is attracted towards the zone in which the electricallycharged condenser surface area is smallest (functioning as in FIG. 2).

FIGS. 4 and 5 illustrate a relay designed to be manufactured with EFABtechnology. This micromechanism manufacturing technology by means oflayer depositing is known by persons skilled in the art, and allows theproduction of several layers and presents a great deal of versatility inthe design of three-dimensional structures. The relay is mounted on asubstrate 1 which serves as support, and which in several of theappended drawings has not been illustrated in the interest ofsimplicity. The relay has a first condenser plate 3 and a fourthcondenser plate 5 arranged on the left (according to FIG. 5) of aconductive element 7, and a second condenser plate 9 and a thirdcondenser plate 11 arranged on the right of the conductive element 7.The relay also has two first stops 13 which are the first contact point15 and the second contact point 17, and two second stops 19 which arethe third contact point 21 and the fourth contact point 23. The relay iscovered in its upper part, although this cover has not been shown inorder to be able to clearly note the interior details.

The relay goes from left to right, and vice versa, according to FIG. 5,along the intermediate space 25. As can be observed the first stops 13and the second stops 19 are closer to the conductive element 7 than thecondenser plates 3, 5, 9 and 11. In this manner the conductive element 7can move from left to right, closing the corresponding electriccircuits, without interfering with the condenser plates 3, 5, 9 and 11,and their corresponding control circuits.

The conductive element 7 has a hollow internal space 27.

There is play between the conductive element 7 and the walls which formthe intermediate space 25 (which is to say the first stops 13, thesecond stops 19, the condenser plates 3, 5, 9 and 11 and the two lateralwalls 29) which is sufficiently small to prevent the conductive element7 from spinning along an axis perpendicular to the plane of the drawingof FIG. 5 enough to contact the first contact point 15 with the thirdcontact point 21 or the second contact point 17 with the fourth contactpoint 23. In the figures, however, the play is not drawn to scale, so asto allow greater clarity in the figures.

FIGS. 6 to 8 show another relay designed to be manufactured with EFABtechnology. In this case the conductive element 7 moves vertically, inaccordance with FIGS. 6 to 8. The use of one or the other movementalternative in the relay depends on design criteria. The manufacturingtechnology consists in the deposit of several layers. In all figures thevertical dimensions are exaggerated, which is to say that the physicaldevices are much flatter than as shown in the figures. Should one wishto obtain larger condenser surfaces it would be preferable to constructthe relay with a form similar to that shown in the FIGS. 6 to 8(vertical relay), whilst a relay with a form similar to that shown inFIGS. 4 and 5 (horizontal relay) would be more appropriate should alesser number of layers be desired. Should certain specific technologiesbe used (such as those usually known as polyMUMPS, Dalsa, SUMMIT,Tronic's, Qinetiq's, etc) the number of layers will always be limited.The advantage of a vertical relay is that larger surfaces are obtainedwith a smaller chip area, and this implies much lower activationvoltages (using the same chip area).

Conceptually the relay of FIGS. 6 to 8 is very similar to the relay ofFIGS. 4 and 5, and has the first condenser plate 3 and the fourthcondenser plate 5 arranged in the lower part (FIG. 8) as well as thesecond stops 19 which are the third contact point 21 and the fourthcontact point 23. As can be seen in the drawings the second stops 19 areabove the condenser plates, such that the conductive element 7 can bearon the second stops 19 without entering into contact with the first andfourth condenser plates 3, 5. In the upper end (FIG. 6) is the secondcondenser plate 9, the third condenser plate 11 and two first stops 13which are the first contact point 15 and the second contact point 17. Inthis case the play between the conductive element 7 and the lateralwalls 29 is also sufficiently small to avoid the first contact point 15contacting with the third contact point 21 or the second contact point17 contacting with the fourth contact point 23.

The relay shown in FIGS. 9 and 10 is an example of a relay in which themovement of the conductive element 7 is substantially a rotation aroundone of its ends. This relay has a first condenser plate 3, a secondcondenser plate 9, a third condenser plate 11 and a fourth condenserplate 5, all mounted on a substrate 1. Additionally there is a firstcontact point 15 and a third contact point 21 facing each other. Thedistance between the first contact point 15 and the third contact point21 is less than the distance between the condenser plates. Theconductive element 7 has a cylindrical part 31 which is hollow, in whichthe hollow is likewise cylindrical. In the interior of the cylindricalhollow is housed a second contact point 17, having a cylindricalsection.

In this manner the conductive element 7 will establish an electricalcontact between the first contact point 15 and the second contact point17 or the third contact point 21 and the second contact point 17. Themovement performed by the conductive element 7 is substantially arotation around the axis defined by the cylindrical part 31. The playbetween the second contact point 17 and the cylindrical part 31 isexaggerated in the FIG. 9, however it is certain that a certain amountof play exists, the movement performed by the conductive element 7 thusnot being a pure rotation but really a combination of rotation andtravel.

From the cylindrical part 31 extends a flat part 33 which has a lesserheight than the cylindrical part 31, measured in the direction of theaxis of said cylindrical part 31. This can be observed in greater detailin FIG. 10, in which is shown a view almost in profile of thecylindrical part 31 and the flat part 33. In this manner one avoids theflat part 33 entering into contact with the substrate 1, which reducesthe frictional forces and sticking.

As can be seen, substituting a parallelepipedic part for the cylindricalpart 31 and replacing the second contact point 17 having a circularsection by one having a quadrangular section, as long as play issufficient, one can design a relay which is conceptually equivalent tothat of FIGS. 9 and 10.

If, for example, in the relay shown in FIGS. 9 and 10 the first contactpoint 15 and/or the third contact point 21 were eliminated, then itwould be the very condenser plates (specifically the third condenserplate 11 and the fourth condenser plate 5) which would serve as contactpoints and stops. By means of a suitable choice of voltages at which thecondenser plates must work one can obtain that this voltage be alwaysVCC or GND. Another possibility would be, for example, that the thirdcontact point 21 were not electrically connected to any externalcircuit. Then the third contact point would only be a stop, and when theconductive element 7 contacts the second contact point 17 with the thirdcontact point 21, the second contact point 17 would be in a state ofhigh impedance in the circuit.

The relay shown in FIG. 11, is designed to be manufactured withpolyMUMPS technology. As already mentioned, this technology is known bya person skilled in the art, and is characterised by being a surfacemicromachining with three structural layers and two sacrificial layers.However, conceptually it is similar to the relay shown in FIGS. 9 and10, although there are some differences. Thus in the relay of FIG. 11the first condenser plate 3 is equal to the third condenser plate 11,but is different from the second condenser plate 9 and the fourthcondenser plate 5, which are equal to each other and smaller than theformer. With respect to the second contact point 17 it has a widening atits upper end which permits retaining the conductive element 7 in theintermediate space 25. The second contact point 17 of FIGS. 9 and 10also can be provided with this kind of widening. It is also worth notingthat in this relay the distance between the first contact point 15 andthe third contact point 21 is equal to the distance between thecondenser plates. Given that the movement of the conductive element 7 isa rotational movement around the second contact point 17, the oppositeend of the conductive element describes an arc such that it contactswith first or third contact point 15, 21 before the flat part 33 cantouch the condenser plates.

FIG. 12 shows another relay designed to be manufactured with polyMUMPStechnology. This relay is similar to the relay of FIGS. 4 and 5,although it has, additionally, a fifth condenser plate 35 and a sixthcondenser plate 37.

FIG. 13 illustrates a relay equivalent to that shown in FIGS. 4 and 5,but which has six condenser plates in the first zone and six condenserplates in the second zone. Additionally, one should note the upper coverwhich avoids exit of the conductive element 7.

FIGS. 14 and 15 illustrate a relay in which the conductive element 7 iscylindrical. Referring to the relay of FIG. 14, the lateral walls 29which surround the conductive element are parallelepipedic, whilst inthe relay of FIG. 15 the lateral walls 29 which surround the conductiveelement 7 are cylindrical. With respect to FIG. 16, it shows a spheremanufactured by means of surface micromachining, it being noted that itis formed by a plurality of cylindrical discs of varying diameters. Arelay with a spherical conductive element 7 such as that of FIG. 16 canbe, for example, very similar conceptually to that of FIG. 14 or 15replacing the cylindrical conductive element 7 by a spherical one.Should be taken into account however certain geometric adjustments inthe arrangement of the condenser plates and the contact points in theupper end, to avoid the spherical conductive element 7 first touchingthe condenser plates and not the contact points or, as the case may be,the corresponding stops.

FIG. 17 shows a variant of the relay illustrated in FIGS. 4 and 5.

In this case the conductive element 7 has protuberances 39 in itslateral faces 41.

FIG. 18 illustrates a variant of the relay according to the invention,specifically designed for use as a detector of Coriolis forces(gyrostat). In this case one can note that the relay has a firstcondenser plate 3 and a fourth condenser plate 5 arranged on the left(in accordance with FIG. 18) of a conductive element 7, and a secondcondenser plate 9 and a third condenser plate 11 arranged on the rightof the conductive element 7. The relay also has two first stops 13,which are the first contact point 15 and the second contact point 17, inthe upper part of FIG. 18, and two second stops 19 which are the thirdcontact point 21 and the fourth contact point 23, in the lower part ofFIG. 18. The conductive element 7 moves in a zigzag fashion between thecondenser plates thanks to voltages applied between such. If the relayis subjected to Coriolis forces the conductive element 7 will be movedlaterally, i.e. upwards or downwards according to FIG. 18 (supposingthat the rotational movement is perpendicular to the plane of drawing).In making contact with the first contact point 15 and the second contactpoint 17 (or the third contact point 21 and the fourth contact point 23,and depending on the speed with which the zigzag is performed (and onthe geometric parameters and the masses of the relay) the Coriolis forcecan be determined and, in consequence, the speed of rotation. The relayalso has third stops 43 and fourth stops 45 which can (additionally andoptionally) also be electric contacts. Thus the end travel of eachzigzag movement is detected by the closing of the corresponding electriccircuit, which is used by the relay control circuit. Alternatively, theposition of the conductive element 7 can be determined by otherprocedures known by a person skilled in the art.

1-37. (canceled)
 38. Miniaturised relay comprising: a first condenser plate, a second condenser plate facing said first condenser plate, in which said second plate is smaller than or equal to said first plate, an intermediate space, a conductive element arranged in said intermediate space, said conductive element being a detached part capable of moving freely along the intermediate space and being suitable for effecting a movement across said intermediate space from a first end of said intermediate space, defining a first zone, to a second end of said intermediate space, defining a second zone, and vice versa, said movement depending on voltages present in said first and second condenser plates, where said first condenser plate is arranged in said first zone and said second condenser plate is arranged in said second zone, a third condenser plate arranged in said second zone, in which said third condenser plate is smaller than or equal to said first condenser plate, and in which said second and third condenser plates are, together, larger than said first condenser plate a first contact point of an electric circuit, a second contact point of said electric circuit, in which said first and second contact points define first stops, in which said conductive element is suitable for entering into contact with said first stops and in which said conductive element closes said electric circuit when in contact with said first stops, where the closing of the external electric circuit can be guaranteed even though the conductor element remains at a voltage in principle unknown, which will be forced by the external circuit that is closed.
 39. Relay according to claim 38, wherein said first contact point is between said second zone and said conductive element.
 40. Relay according to claim 38, wherein said second contact point is likewise in said second zone.
 41. Relay according to claim 38, further comprising: a fourth condenser plate arranged in said first zone, in which said first condenser plate and said second condenser plate are equal to each other, and said third condenser plate and said fourth condenser plate are equal to each other.
 42. Relay according to claim 41, wherein said first, second, third and fourth condenser plates are all equal to each other.
 43. Relay according to claim 41, further comprising: a fifth condenser plate arranged in said first zone and a sixth condenser plate arranged in said second zone, in which said fifth condenser plate and said sixth condenser plate are equal to each other.
 44. Relay according to claim 43 further comprising: six condenser plates arranged in said first zone and six condenser plates arranged in said second zone.
 45. Relay according to claim 38, further comprising: a second stop between said first zone and said conductive element.
 46. Relay according to claims 38, further comprising: a third contact point arranged between said first zone and said conductive element, in which said third contact point defines a second stop, such that said conductive element closes a second electric circuit when in contact with said second contact point and said third contact point.
 47. Relay according to claim 46, wherein said conductive element comprises a hollow cylindrical part which defines an axis, in the interior of which is housed said second contact point, and a flat part which protrudes from one side of said radially hollow cylindrical part and which extends in the direction of said axis, in which said flat part has a height, measured in the direction of said axis, which is less than the height of said cylindrical part measured in the direction of said axis.
 48. Relay according to claim 46, wherein said conductive element comprises a hollow parallelepipedic part which defines an axis, in the interior of which is housed said second contact point, and a flat part which protrudes from one side of said radially hollow paralelepipedic part and which extends in the direction of said axis, in which said flat part has a height, measured in the direction of said axis, which is less than the height of said parallelepipedic part, measured in the direction of said axis.
 49. Relay according to claim 38, further comprising: a third contact point and a fourth contact point arranged between said first zone and said conductive element, in which said third contact point and fourth contact point define second stops, such that said conductive element closes a second electric circuit when in contact with said third contact point and fourth contact point.
 50. Relay according to claim 38, wherein assemblies of said condenser plates are each arranged in each of said first and second zones to have a central symmetry with respect to a center of symmetry, and in which said center of symmetry is superposed to the center of masses of said conductive element.
 51. Relay according to claims 38, wherein an assembly of said condenser plates arranged in each of said first and second zones has central asymmetry, thus generating a moment of forces with respect to the center of masses of said conductive element.
 52. Relay according to claim 49,wherein between said first zone and said second zone there extends two lateral walls, in which there is play between said lateral walls and said conductive element, said play being sufficiently small so as to geometrically prevent said conductive element from simultaneously entering into contact with a contact point of the group formed by said first and second contact points and with a contact point of the group formed by said third and fourth contact points.
 53. Relay according to claim 38, wherein said conductive element has rounded external surfaces.
 54. Relay according to claim 53, wherein said conductive element is cylindrical.
 55. Relay according to claim 53, wherein said conductive element is spherical.
 56. Relay according to claim 38, wherein said conductive element has an upper face and a lower face, said upper and lower faces being perpendicular to said movement of said conductive element, and at least one lateral face, in which said lateral face has slight protuberances.
 57. Relay according to claim 38, wherein said conductive element is hollow.
 58. Relay according to claim 38, wherein said first condenser plate has a surface area which is equal to or double the surface area of said second condenser plate.
 59. Relay according to claim 38, wherein said condenser plates is, simultaneously one of said contact points.
 60. Use of a relay according to claim 38, as an accelerometer.
 61. Use of a relay according to claim 38, as an accelerometer in airbags.
 62. Use of a relay according to claims 38, as a tiltmeter.
 63. Use of a relay according to claim 38, as a detector of Coriolis forces.
 64. Use of a relay according to claim 38, as a pressure sensor.
 65. Use of a relay according to claim 38, as a microphone.
 66. Use of a relay according to claim 38, as a flow sensor.
 67. Use of a relay according to claim 38, as a temperature sensor.
 68. Use of a relay according to claim 38, for an acoustic applications.
 69. Use of a relay according to claim 38, as a gas sensor.
 70. Use of a relay according to claim 38, as a magnetic field sensor. 